1. Field of the Invention
The present invention relates to a flip-chip type semiconductor device and its manufacturing method, and more particularly, to the improvement of reducing stress strain within the flip-chip type semiconductor device.
2. Description of the Related Art
Recently, flip-chip type semiconductor devices have been developed to meet the requirements of higher performance, smaller and lighter size and higher speed for electronic equipment.
Generally, a flip-chip type semiconductor device having metal bumps is directly mounted on a motherboard having electrodes corresponding to the metal bumps. That is, if the metal bumps are solder balls, the solder balls are reflown and soldered on the motherboard. In this case, a stress strain occurs due to the discrepancy in thermal expansion coefficient between the semiconductor device and the motherboard, which would deteriorate the reliability characteristics of the semiconductor device. This will be explained later in detail.
In order to minimize the above-mentioned discrepancy in thermal expansion coefficient, the motherboard is made of ceramic material such as aluminum nitride (AlN), mullite or glass ceramics, which have a thermal expansion coefficient close to that of silicon. In this case, however, the motherboard becomes more expensive, and therefore, its application is limited to high-priced equipment such as a super computer and a large scale computer.
On the other hand, in order to disperse shearing stress occurring at the metal bumps to substantially reduce the above-mentioned stress strain, under-fill resin is inserted between the semiconductor device and the motherboard (see JP-A-9-92685). In this case, however, if voids may be generated within the under-fill resin or if the adhesive characteristics between the under-fill resin and the semiconductor device (or the motherboard) deteriorate, the semiconductor device would be separated from the motherboard.
In other approaches to disperse shearing stress occurring at the metal bumps to substantially reduce the above-mentioned stress strain, an elastic layer made of rubber or expandable styrene is provided on the semiconductor device (see JP-A-11-40613, JP-A-11-74309). This also will be explained later in detail.
In the above-mentioned approaches, however, since the elastic layer includes much contamination, the reliability of the semiconductor device would deteriorate.
It is an object of the present invention to provide a reliable flip-chip type semiconductor device and its manufacturing method.
According to the present invention, in a flip-chip type semiconductor device, a plurality of pad electrodes are formed on a semiconductor substrate. An insulating stress-absorbing resin layer made of thermosetting resin is formed on the semiconductor substrate and has openings corresponding to the pad electrodes. A plurality of flexible conductive members are filled in the openings. A plurality of metal bumps are formed on the flexible conductive layers.
Since the thermosetting resin has little contamination, the reliability of the flip-chip type semiconductor device would be improved.